Duck and cover is a method of personal protection against the near prompt effects of a nuclear explosion. It is useful in conferring a degree of protection to practitioners outside the radius of the nuclear fireball but still within sufficient range that by standing upright death or serious injury is certain. As a countermeasure to the lethal effects of nuclear explosions, it is most effective in the event of both a surprise nuclear attack, which might come at any time without warning,[note 1] and in the more likely event of sufficient warning of a few seconds to minutes given by a system such as the Pinetree Line, but not enough advance notice to permit an effective evacuation.

Contents

Subject matter[edit]

Under the conditions of a surprise attack, immediately after one sees the nuclear flash, one should stop and get on the ground under some cover—such as a table, or at least next to a wall—and assume a prone like position, lying face-down and covering exposed skin and the back of ones head with ones clothes, or if no excess clothes such as a coat is available, to cover the back of ones head with hands. Similar instructions as presented in the Duck and Cover (film) are contained in the British 1964 Civil Defence Information Bulletin No. 5 film.[1] and in the 1980s Protect and Survive TV series.[2]

Under the conditions where some warning is given, one is advised to find the nearest Civil Defense shelter, or if one could not be found, any well-built building to stay and shelter in.

Proponents of duck and cover argue that thousands could be saved by following the simple advice, without which, to give one easily understand example, people, being naturally inquisitive, would instead run to windows to try to locate the source of the immensely bright flash generated at the instant of the explosion. During which time, unbeknownst to them, the slower moving blast wave would rapidly be advancing toward their position, only to arrive and cause a window glass implosion, shredding onlookers.[3]

In the Testimony of Dr. Hiroshi Sawachika for example, although he was sufficiently far away from the Hiroshima bomb himself and not behind a pane of window glass when the blast wave arrived, those in his company who were, had serious blast injury wounds, with broken glass and pieces of wood stuck into them.[4]

According to the 1946 book Hiroshima and other books which cover both bombings,[5] in the days between the atomic bombings of Hiroshima and Nagasaki in Japan during World War II, some survivors of the first bombing went to Nagasaki and taught others about ducking after the atomic flash and particularly the dangers of window glass. As a result of this timely warning, far fewer of those informed by them in Nagasaki died in the initial blast when compared to those who were in in similar surroundings but were caught completely unaware. The general population was not warned of the heat/blast danger following an atomic flash because of the bomb’s new and unknown nature. Many people in Hiroshima and Nagasaki died while searching the skies curiously for the source of the brilliant flash.

When people are indoors, running to windows to investigate the source of bright flashes in the sky still remains a common inquisitive human response to experiencing a flash, so although the advice to duck and cover is over half a century old, ballistic glass lacerations caused the majority of the 1000 human injuries following the Chelyabinsk meteorair burst of February 15, 2013.[6] This natural human behavior was also observed amongst people in the vicinity of Hiroshima and Nagasaki, and therefore a human behavior advised against in duck and cover advice, and in the film of the same name.[7][8]

The dangers of viewing explosions behind common window glass was known of before the nuclear age began, being a common source of injury and death from large chemical explosions, with one such incident being the 1944 Port Chicago explosion, where about 4,600 tons (4,173 metric tons)[9] of chemical explosive accidentally detonated in a series of events. Survivor, Robert Routh, reported enjoying the sight of the wonderfully bright fireball and then suddenly never seeing anything again, as following the blast arriving, he was permanently blinded by the window he was viewing the fireball from, shards of which pierced his eyes and face.[10]

Similar to duck and cover is the advice to "Drop, Cover and Hold On" which is taught in areas prone to earthquakes. Schools in some tornado-prone areas of the United States also practice tornado drills that involve children squatting and covering the backs of their heads.[11][12]

Assessment[edit]

1954 test shot Nectar of Operation Castle produced a yield of 1.69 megatons and was conducted off the coast of Teiter island. Note the distinctive near instantaneous double flash, with the second appearing brighter than the sun, and the blast wave slowly, by comparison, spreading out turning the calm ocean water a frothy white when it arrives. The maximum average nuclear fireball radius is approximately 1.4 to 1.6 km (0.87 to 0.99 mi).[14][15] The outdoor blast and flash burnLD50s would be around 8 and 12 km respectively.[14][16] Assuming personnel did not take any prompt countermeasures, instead standing still absorbing the entire light energy emitted over the ~20 seconds of emission.

Within a considerable radius from the surface of the nuclear fireball, 0–3 kilometers—largely depending on the explosion's height, yield and position of personnel—ducking and covering would offer negligible protection against the intense heat, blast and prompt ionizing radiation following a nuclear explosion. Beyond that range, however, many lives would be saved by following the simple advice,[17] especially since at that range the main hazard is not from ionizing radiation but from blast injuries and sustaining thermal flash burns to unprotected skin.[16][18][19][20] Furthermore, following the bright flash of light of the nuclear fireball, the explosion's blast wave would take from first light, 7 to 10 seconds to reach a person standing 3 km from the surface of the nuclear fireball, with the exact time of arrival being dependent on the speed of sound in air in their area.[21][22][23] The time delay between the moment of an explosions flash and the arrival of the slower moving blast wave is analogous to the commonly experienced time delay between the observation of a flash of lightning and the arrival of thunder during a lightning storm, thus at the distances that the advice would be most effective, there would be more than ample amounts of time to take the prompt countermeasure of 'duck and cover' against the blast's direct effects and flying debris.[24] For very large explosions it can take 30 seconds or more, after the silent moment of flash, for a potentially dangerous blast wave over-pressure to arrive at, or hit, your position.[25]

It must be kept in mind that the graphs of lethal ranges as a function of yield, that are commonly encountered,[16][18] are the unobstructed "open air", or "free air" ranges that assume amongst other things, a perfectly level target area, no passive shielding such as attenuating effects from urban terrain masking, e.g. skyscraper shadowing, and so on. Therefore they are thus considered to present an overestimate of the lethal ranges that would be encountered in an urban setting in the real world.[26] With this being most evident following a ground burst with explosive yield similar to first generation nuclear weapons.[26][27]

To highlight the effect that being indoors, and especially below ground can make, despite the lethal open air radiation, blast and thermal zone extending well past her position at Hiroshima,[18] Akiko Takakura survived the effects of the 16 kt atomic bomb at a distance of 300 meters from ground zero, sustaining only minor injuries, due in greatest part to her position in the lobby of the Bank of Japan, a reinforced concrete building, at the time of the nuclear explosion,[28][29] and to highlight the protection conferred to an individual who is below ground during a nuclear air burst, Eizo Nomura survived the same blast at Hiroshima at a distance of 170 meters from ground zero.[30] Nomura, who was in the basement of what is now known as the rest house, also a reinforced concrete building,[30] lived into his early 80s.[31][32][33]

In contrast to these cases of survival, the unknown person sitting outside on the steps of the Sumitomo Bank next door to the Bank of Japan on the morning of the bombing—and therefore fully exposed—suffered what would have eventually been lethal third-degree burns from the near instant nuclear weaponflash if they hadn't then promptly been killed by the slower moving blast wave, when it reached them, ~1 second later.[34]

To elucidate the effects on lying flat on the ground in attenuating a weapons blast, Miyoko Matsubara, one of the Hiroshima maidens, when recounting the bombing in an interview in 1999, said that she was outdoors and less than 1 mile from the hypocenter of the Little Boy bomb. Upon observing the nuclear weapons silent flash she quickly lay flat on the ground, while those who were standing directly next to her, and her other fellow students, had simply disappeared from her sight when the blast wave arrived and blew them away.[35][36][37]

Position of the body can have a considerable influence in protection from blast effects. Lying prone on the ground will often materially lessen direct blast effects because of the protective defilade effects of irregularities in the ground surface. Ground also tends to deflect some of the blast forces upward. Standing close to a wall, even on the side from which the blast is coming, also lessens some of the effect. Orientation of the body also affects severity of the effect of blast. Anterior exposure of the body may result in lung injury, lateral position may result in more damage to one ear than the other, while minimal effects are to be anticipated with the posterior surface of the body (feet) toward the source of the blast.[38]

The human body is more resistant to sheer overpressure than most buildings, however, the powerful winds produced by this overpressure, as in a hurricane, are capable of throwing human bodies into objects or throwing objects at high velocity, both with lethal results, rendering casualties highly dependent on surroundings.[17][39] For example, Sumiteru Taniguchi recounts that, while clinging to the tremoring road surface after the fat man detonation, he witnessing another child being blown away, the destruction of buildings around him and stones flying through the air.[40] Similarly, Akihiro Takahashi and his classmates were blown by the blast of Little Boy by a distance of about 10 meters, having survived due to not colliding with any walls etc. during his flight through the air,[41] Likewise, Katsuichi Hosoya has a near identical testimony.[42]

During the 2013 Chelyabinsk meteor explosion, a fourth-grade teacher in Chelyabinsk, Yulia Karbysheva, saved 44 children from potentially life-threatening ballistic window glass cuts by ordering them to hide under their desks when she saw the flash. Despite not knowing the origin of the intense flash of light, she ordered her students to execute a duck and cover drill. Ms. Karbysheva, who herself did not duck and cover but remained standing, was seriously lacerated when the explosion's blast wave arrived, and window glass blew in, severing a tendon in one of her arms; however, not one of her students, who she ordered to hide under their desks, suffered a cut.[43] A follow up study of the effects of the meteor airburst determined that the windows most prone to breaking when exposed to a blast overpressure are those of school buildings, which tend to be large in area.[44]

While the bombings of Hiroshima and Nagasaki demonstrated that the urban area of glass breakage is nearly 16 times greater than the area of significant structural/building damage, although improved building codes since then may contribute to better building survival, there would be a higher likelihood of glass breakage and therefore potential injury/death for people near windows because many modern buildings have larger windows.[45]

Anything that can cast a shadow will protect that which is shadowed from being burnt. [46] In this case a valve protecting a portion of the wall of a gas holder from having a line-of-sight with the nuclear fireball whereas all un-shadowed painted surfaces were lightened.[47] A large number of these permanent markings were used, by extrapolating backward, to determine the exact point of detonation in the sky.[48][49][50]

A man who was present at Nagasaki on August 9, 1945 during the dropping of the 20-kiloton Fat Man bomb, this photo displays that 1st- and 2nd-degree burn injuries he experienced on his unclothed skin, the shoulder and arm, while the thin vest garment of clothing that he was wearing at the time of the explosion completely protected his stomach and lower chest from experiencing similar burns. A clearer color restored version of this picture is also available.[51]

The advice to cover one's exposed skin with anything that can cast a shadow, like the picnic blanket and newspaper used by the family in the film, may seem absurd at first when one considers the capabilities of a nuclear weapon, but even the thinnest of barriers such as cloth or plant leaves would reduce the severity of burns on the skin from the thermal radiation( the thermal radiation/flash is light, similar in average emission spectrum/color to sun light,[52] emitting in the ultraviolet, visible light, and infrared range but with a higher light intensity than sunlight, with this combination of light rays capable of delivering radiant burning energy to exposed skin areas.[53] While the duration of emittance of this burning thermal radiation, which can be experienced by people within range, increases with yield, it is usually at least a few seconds long.[54]) A photograph taken about 1.3 km from the hypocenter of the Hiroshima bomb explosion showed that the shadowing effect of leaves from a nearby shrub protected a wooden utilities pole from charring discoloration due to thermal radiation, while the rest of the telephone pole, not under the protection of the leaves, was charred almost completely black.[55]

The advice to "duck and cover" holds well in many situations where structural destabilization or debris may be expected, such as during an earthquake or tornado. At a sufficient distance from a nuclear explosion, the blast wave would produce similar results and ducking and covering would perhaps prove adequate. It would also offer some protection from flying glass and other small, but dangerous, debris. Ducking and covering would also slightly reduce exposure to the initial gamma rays, particularly the portion emitted after the flash.[56] These initial gamma rays are emitted from the fireball & following mushroom cloud and can reach personnel on the ground for a total of approximately 1 minute.[57] Since gamma rays are mostly emitted in a straight line, people laying on the ground will have a higher chance to have obstacles serving as radiation protection such as building walls, foundations, car engines, etc. between their bodies and the radiation emitted from the initial fireball and the accompanying lower level of radiation still being emitted through to the beginning of the mushroom cloud phase, known as "cloudshine",[58] or that down scattered by the air/"skyshine".[59]

The technique offers a small protection against fallout, however it must be said that the technique assumes that after the blast and initial radiation effects subside, with the latter of which being no longer a concern after about "twenty seconds" to 1 minute post detonation,[57][60] a person who ducks and covers will realize when it is wise to cease ducking and covering (after the blast and initial radiation danger has passed) and to then seek out a more sheltered area, like an established or improvized fallout shelter to protect themselves from the ensuing potential local fallout danger. If such a shelter is unavailable, at this point the person is advised to follow the Shelter in Place protocol, or if given, Emergency evacuation advice. Evacuation orders would entail exiting the area completely by following a path perpendicular to the wind direction, and therefore perpendicular to the path of the fallout plume.[61] While "sheltering in place" is staying indoors, in a preferably sealed tight basement, or internal room, for a number of hours, with the oxygen supply available in such a scenario being more than sufficient for 3+ hours in even the smallest average room, under the assumption that the improvised seal is perfect, until carbon dioxide levels begin to reach unsafe values and necessitate room unsealing for a number of minutes to create a room air change.[62][63]

After all, "Duck and Cover" is a first response countermeasure only, in much the same way that "Drop, Cover and Hold On" is during an earthquake, with the advice having served its purpose once the earthquake has passed, and possibly other dangers—like a tsunami—may be looming.

In the era the advice was originally given, the most common nuclear weapons were weapons comparable to the US Fat Man and Soviet Joe-1 in yield. The most far reaching dangers that initially come from the nuclear explosion of this, and higher, yield weapons as airbursts, are the initial flash/heat and blast effects and not from fallout. This is due to the fact that when nuclear weapons are detonated to maximize the range of building destruction, that is, maximize the range of surface blast damage, an airburst is the preferred nuclear fuzing height, as it exploits the mach stem phenomenon. This phenomenon of a blast wave occurs when the blast reaches the ground and is reflected. Below a certain reflection angle the reflected wave and the incident wave merge and form a reinforced horizontal wave, this is known as the 'Mach stem' (named after Ernst Mach) and is a form of constructive interference and consequently extends the range of high pressure.[64][65][66][67] Airburst fuzing, as one would expect, increases the range that peoples skin will have a line-of-sight with the nuclear fireball. However as a result of the high altitude of the explosion, most of the radioactive bomb debris/ is dispersed into the stratosphere, with a great column of air therefore placed between the vast majority of the bomb debris/fission reaction products and people on the ground for a number of crucial days before it falls out of the atmosphere in a comparatively dilute fashion, this "delayed fallout" is henceforth not an immediate concern to those near the blast. On the other hand, the only time that fallout is rapidly concentrated in a potentially lethal fashion in the local/regional area around the explosion is when the nuclear fireball makes contact with the ground surface, with an explosion that does so, being aptly termed a surface burst.[68] For example in the Operation Crossroads tests of 1946 on Bikini Atoll, using two explosive devices of the same design and yield, the first, Test Able (an air burst) had little local fallout, but the infamous Test Baker a near surface shallow (underwater burst) left the local test targets badly contaminated with radioactive fallout.

Widespread radioactive fallout itself was not recognized as a threat amongst the public at large before 1954, until the widely publicized story of the 15 megaton surface burst of the experimental test shot Castle Bravo on the Marshall Islands. The explosive yield of the Castle Bravo device the Shrimp was unexpectedly high, and therefore correspondingly higher amounts of local fallout were produced. When this arrived at their location carried by the wind, this caused the 23 crew members on a Japanese fishing boat known as the Lucky Dragon to come down with acute radiation sickness with varying degrees of seriousness and due to complications in the treatment of the ship's radio operator months after the exposure, resulted in his death.

It is, however, unlikely that a well-funded belligerent with nuclear weapons would waste their weapons with fuzing to explode below or on the surface, as both test shot Baker, and Castle Bravo were respectively. Instead, to maximize the range of city blast destruction and immediate death, an air burst is preferred,[68] as the ~ 500 meter explosion heights of the only nuclear weapons used on cities, Little Boy and Fat Man also attests to.[69] Moreover, with air bursts the total amount of radiation contained in the fallout, in units of activity/Becquerel, is somewhat less than the total that would be released from a surface or subsurface burst, as in comparison, depending on the height of burst, little to no neutron activation or neutron induced gamma activity of soil occurs from air bursts.[70] Therefore the initial danger from concentrated local/'early' fallout (which takes on the color of the soil around the fireball, commonly with a dusty pumice or ash-like appearance, as experienced by the crew of the Lucky Dragon) remains low in a global nuclear war scenario. Instead the fallout most likely to be encountered by most survivors in this scenario is expected to be the less dangerous but widely spread global/'late' fallout.[71] As an air burst at optimum height will produce a negligible amount of early fallout.[72]

A notable comparison to underline this is found when one compares the 50 megaton airburst Tsar Bomba, which produced no concentrated local/early fallout, and thus no known deaths from radiation, with the surface burst of the 15 megaton Castle Bravo, which in comparison, due to the local fallout produced, was implicated in the death of 1 of 23 crew on the Lucky Dragon and made the entire Bikini Atoll unfit for further nuclear testing until enough time elapsed and the intensity of the radiation field had decayed to acceptable levels.[note 2]

An operation Doorstep mother and daughter Mannequin in an improvised basement lean-to shelter prior to testing in test shot Upshot-Knothole Annie. To Shelter-in-place in such an area would offer, in a number of outdoor dose rates, an adequate fallout radiation protection factor(PF) or "dose reduction factor" of 20 or more.[73] More effective basement spaces did/do exist however, of "10 million" homes assessed in 1968, 500,000 US basements were found to have a PF-40.[74][75]

Furthermore, regardless of if a nuclear attack on a city is of the surface or air-burst variety or a mixture of both, the advice to shelter in place, in the interior of well-built homes, or if available, fallout shelters, as suggested in the film Duck and Cover, will drastically reduce ones chance of absorbing a hazardous dose of radiation.[76] A real world example of this occurred after the Castle Bravo test where, in contrast to the crew of the Lucky Dragon, the firing crew that triggered the explosion safely sheltered in their firing station until after a number of hours had passed and the radiation levels outside fell to dose rate levels safe enough for an evacuation to be considered.[77][78] The comparative safety experienced by the Castle Bravo firing crew served as a proof of concept to civil defense personnel that Shelter in place (or "buttoning up" as it was known then) is an effective strategy in mitigating the potentially serious health effects of local fallout.[77]

The minimum typical protection factor of the fallout shelters in US cities is 40 or more, in many cases these shelters are nothing more than the interior of pre-existing well-built buildings that have been inspected, and following their protection factors being calculated, re-purposed as fallout shelters.[79][80][81][82]

A protection factor of at least 40 means that the Radiation shielding provided by the shelter reduces the radiation dose experienced by at least 40 times that which would be experienced outside the shelter with no shielding. "Protection factor" is equivalent to the modern term "dose reduction factor".[83]

In units of Rads, this is a simplistic model(Gaussian) of a wind blown fallout map,[45] which depicts the unshielded ground level fallout gamma ray dose and dose rate contours expected to follow a 2 megaton land surface burst detonation, with 1 megaton of the yield coming from fission reactions. Because of radioactive decay, the dose rate contours (on the right) contract after fallout has arrived, but the total absorbed dose contours (left) continue to grow. A similar color version of the right panel, dose rate contour plot, for a 0.1 to 10 kiloton surface burst is also available.[84]Acutely dangerous regions of fallout are accompanied by fallout particles which are large enough to be detected by eye during its falling out/deposition, that is, they are equal to or larger than the size of dust.[45][85]

During the first hour after a nuclear explosion, radioactivity levels drop precipitously. Radioactivity levels are further reduced by about 90% after another 7 hours and by about 99% after 2 days.[61] An accurate rule of thumb for approximating the radioactive dose rate produced by the decay of the myriad of isotopes present in nuclear fallout is the "7/10 rule". The rule states that for each 7 fold increase in time the dose rate drops by a factor of 10.[86] For example, assuming the fallout process has ended and the dose rate is a lethal in one hour exposure, 500 roentgens per hour, at one hour after detonation, then 7 hours after detonation the rate will be 50 R/hr, 49 hours after detonation (7×7 hours) the dose rate will be 5 R/hr, 343 hours after detonation (49×7—or about 2 weeks) the dose rate will be about 0.5 R/hr, at which point no special precautions would need to be taken and venturing outside into that dose rate for an hour or two would pose a close to negligible health hazard,[87] thus permitting an evacuation to be done with acceptable safety to a known contamination free zone. Following a nuclear detonation approximately 80 percent of the fallout would be deposited on the ground during the first 24 hours.[25]

“

Dropping immediately and covering exposed skin provide[s] protection against blast and thermal effects....Immediately drop facedown. A log, a large rock, or any depression in the earth's surface provides some protection. Close eyes. Protect exposed skin from heat by putting hands and arms under or near the body and keeping the helmet on. Remain facedown until the blast wave passes and debris stops falling. Stay calm, check for injury, check weapons and equipment damage, and prepare to continue the mission.

Some agencies that promoted “evacuate immediately” guidance as a response to potentially lethal fallout arriving, advice which may have been influenced by these agencies assuming simplistic single wind driven cigar/Gaussian shaped fallout contours would be representative of reality, have since retracted this advice, as this can actually result in higher radiation exposures as it would put people outdoors and in harm’s way when the radiation levels would be highest. The Modeling and Analysis Coordination Working Group (MACWG)-which was set up to resolve conflicting advice given by various agencies, has reaffirmed that the best blanket advice that would reduce the number of casualties by the greatest amount is: "Early, adequate sheltering followed by informed, delayed evacuation."[45]

Expert advice published in the 2010 document Planning Guidance for Response to a Nuclear Detonation is to shelter in place, in an area away from building fires, for at least 1 to 2 hours following a nuclear detonation and fallout arriving,[89] with the greatest benefit, assuming personnel are in a building with a high protection factor, is sheltering for no less than 12 to 24 hours before evacuation.[24] Therefore, sheltering for the first few hours can save lives.[90] Indeed death and injury from local fallout is regarded by experts as the most preventable of all the effects of a nuclear detonation, being simply dependent on if personnel know how to identify an adequate shelter when they see one and enter one quickly, with the number of potential people saved being cited as in the hundreds of thousands.[91][92][93][94] Or even higher if the remaining occupants of the city are made aware of the contaminated areas, by emergency systems, within hours of the events aftermath.[93][95] In 2009-2013 a further iteration on sheltering in place was made to determine the optimal improvized fallout shelter residence times following a nuclear detonation, with computer analysis, it was found individuals should quickly get into the best intact building at least under 5 minutes distant in travel time following the detonation and they should stay there for at least 30 minutes before venturing out to find a shelter with a higher protection factor but that is a greater travel time away +10 minutes.[96][97][98] However although this would be effective in cases were the initial building protection factor is less than about 10, it would require a high degree of individual situational awareness that may be optimistic following the shock of a nuclear detonation, in any case, if a building with a PF of 20 or more is nearby, such as the fallout shelters depicted in the film, in the vast majority of fallout circumstances, it would not be advisable to leave it until 3+ hours have elapsed following the initial arrival of the local fallout.[93][94]

Following a single IND(improvized nuclear device) detonation in the US, the National Atmospheric Release Advisory Center(NARAC) would, within minutes to at most hours, after the detonation have a reliable prediction of the fallout plume size and direction, and when armed with this prediction would then begin attempting to corroborate this with readings from radiation survey meter equipment that would fly over close to the ground in the affected area by means of helicopter or drone(UAV) aircraft that would also follow within tens of minutes to at most hours after the detonation,[note 3] Once a general outline and direction of the fallout is determined, the next step is to disseminate this information to citizens sheltering-in-place by loudspeaker, radio, cell phone etc., with a “Fallout App” containing maps for smart phones being regarded as an area of interest so that survivors don't inadvertently evacuate downwind further into harms way.[99][100]

In respect to the other non-lethal weapon effects from an IND detonated on or near the surface, the detonation's blast wave would likely produce a momentary electric grid blackout due to the loss of a large portion of a cities electrical equipment drawing power/electrical load, while the electromagnetic pulse(EMP) from a surface/ground-burst explosion would cause little damage outside the blast area, so cell phone towers that survive the blast should be capable of carrying communications.[99] Although if communications during the 9/11 attacks or after a major hurricane are anything to go by, and the cell phone network towers survive, the service would be overloaded(a Mass call event) and thereby made useless soon after, however if prior arrangements between the cell network and emergency responders are made to give them priority and bar access to all other individuals, then it may be an effective service. However as Civil defense(CD) shelters, as depicted in the film, were stocked for such an eventuality, they contained amongst other things, at least one CDV-715 survey meter and a CD emergency radio receiver to remain updated on the situation as it developed.

Some historians have thus far sought to dismiss civil defense advice as mere propaganda, despite, as other historians have found, detailed scientific research programs laying behind the much-mocked government civil defense pamphlets of the 1950s and 1960s, including the prompt advice of ducking and covering.[82]

In U.S. Army training, soldiers are taught to fall immediately down, covering face and hands in much the same way as is described by the advice to duck and cover.[101]

The exercises of Cold War civil defense are seen by historian Guy Oakes in 1994, as having less practical use than psychological use: to keep the danger of nuclear war high on the public mind, while also attempting to assure the American people that something could be done to defend against nuclear attack.[102] However, according to contemporary Cold War civil defense pamphlets, like Civil Defence why we need it released in 1981, civil defense countermeasures were presented as analogous to seat belts, and that the suggestion that knowing what steps to take in the "slight" possibility that a nuclear explosion occurs in your region, keeps such calamities high on the public mind, is "like saying people who wear seat belts are expecting to have more crashes than those who do not", and as with a seat belt, there is never a suggestion that if the countermeasure were implemented, it would save everyone. Moreover civil defense was not solely a US-UK or nuclear club phenomenon, countries with long histories of neutrality, such as Switzerland, are "foremost in their civil defence precautions."[103] The Swiss civil defense network has an overcapacity of nuclear fallout shelters for the country's population size, and by law, new homes must still be built with a fallout shelter as of 2011.[104][105]

Tornadoes[edit]

Students participate in a tornado drill, lining up along an interior wall and covering their heads. Tornado drills are an important element in tornado preparedness. Similar to other evidence based safety drills, they teach effective countermeasures and therefore increase survival rates if/when a tornado hits.

Ducking and covering does have certain applications in other, more natural disasters. In states prone to tornadoes, school children are urged to "duck and cover" against a solid inner wall of a school, if time does not permit seeking better shelter—such as a storm cellar—during a tornado warning. The tactic is also widely practiced in schools in states along the West Coast of the United States, where earthquakes are commonplace. Ducking and covering in either scenario would theoretically afford significant protection from falling or flying debris.

Earthquakes[edit]

In an earthquake, (which are generally of a natural tectonic plate origin although they can be artificially generated by the detonation of a nuclear explosive device in which sufficient energy is transmitted into the ground, with an extreme case to serve as an example of this phenomenon being the Operation GrommetCannikin test of the 5 megaton W71 warhead exploded deep underground on Amchitka Island in 1971, which produced a seismic shock quake of 7.0 on the Richter scale) people are encouraged, regardless of the cause of the quake, to "drop, cover, and hold on": to get underneath a piece of furniture, cover their heads and hold on to the furniture. This advice also encourages people not to run out of a shaking building, because a large majority of earthquake injuries are due to broken bones from people falling and tripping during shaking. While it is unlikely that "drop, cover and hold on" will protect against a building collapse, buildings built in earthquake-prone areas in the United States are usually built to earthquake Life Safety Building codes,[106][107][108][109] and thus a building collapse of these structures (even during an earthquake) is rare. "Drop, cover and hold on" may not be appropriate for all locations or building types, but the red cross advises,[110] it is the appropriate emergency response to an earthquake in the United States.

^By 1958, a total of 23 nuclear devices were exploded on or near the atoll,[1] with the majority occurring after the 1954 Operation Castle series, resulting in a total of about 42 megatons of pure fission product fallout being generated around the atoll, this made permanent aboveground habitation without remediation unwise for a decade or so, it was thus resettled in 1968. The inhabitants lived there again from 1968 to 1978, abandoning the atoll in 1978. As of 2014, the Atoll has had infrequent inhabitants since the 1990s, mainly for tours, a return to permanent safe habitation would require locally produced and consumed plant food to be grown with fertilizer, or alternatively, only imported plant food to be eaten.[2][3]

^As this ground hugging fly over has the potential to be mistaken for airlift rescue attempts, which are common after other natural disasters, survivors should not exit shelter unless absolutely necessary in the time period before being informed of the fallout situation, or alternatively, stay in shelter until sufficient time has elapsed, +24 hrs for a delayed evacuation to take place.

See related[edit]

Stop, drop and roll - Advice for when one is on fire and no other means of extinguishing the flames are available.

A Day Called X a dramatized 1957 CBS documentary following the evacuation drill of the entire city of Portland Oregon per Civil Defense protocol, in response to the RADAR detection of an en-route Soviet nuclear bomber force.

^Connor, Shane (24 August 2006). "The good news about nuclear destruction". WND.com. "Thousands can be saved employing the old "Duck and Cover" tactic, without which most people will instead run to the nearest window to see what the big flash was just in time to be shredded by the glass imploding inward from the shock wave."

^"The Good News About Nuclear Destruction, By Shane Connor". "...most can save themselves by immediately employing the 'Duck & Cover' tactic, rather than just allowing an impulsive rush to the nearest windows to see what that 'bright flash' was across town, just-in-time to be shredded by the glass imploding inward from that delayed shock wave blast."

^ ab"The Nuclear Matters Handbook". "Individuals who sense a blinding white flash and intense heat coming from one direction should immediately fall to the ground and cover their heads with their arms. This provides the highest probability that the air blast will pass overhead without moving them laterally and that debris in the blast wave will not cause impact or puncture injuries. Exposed individuals who are very close to the detonation have no chance of survival. At distances at which a wood frame building can survive, however, exposed individuals significantly increase their chance of survival if they are on the ground when the blast wave arrives and if they remain on the ground until after the negative phase blast wave has moved back toward ground zero"

^"The Nuclear Matters Handbook". "Initially, this blast wave moves at several times the speed of sound, but it quickly slows to a point at which the leading edge of the blast wave is traveling at the speed of sound, and it continues at this speed as it moves farther away from ground zero"

^"Nuclear Matters Handbook". "Initially, this blast wave moves at several times the speed of sound, but it quickly slows to a point at which the leading edge of the blast wave is traveling at the speed of sound, and it continues at this speed as it moves farther away from ground zero."

^Original caption: "Shadow" of band valve wheel on paint of a gas holder at Hiroshima. Radiant heat instantly burned paint where the heat rays were not obstructed. 6,300 feet from ground zero (Japanese photo). United States Strategic Bombing Survey, The Effects of Atomic Bombs on Hiroshima and Nagasaki (United States Government Printing Office: Washington, 1946) Chapter 3.

^Malik (1985) describes how various values were recorded for the B-29's altitude at the moment of bomb release over Hiroshima. The strike report said 30,200 ft, the official history said 31,600 ft, Commander Parson's log entry was 32,700 ft, and the navigator's log was 31,060 ft—the latter possibly an error transposing two digits. A later calculation using the indicated atmospheric pressure arrived at the figure of 32,200 ft. Similarly, several values have been reported as the altitude of the Little Boy bomb at the moment of detonation. Published sources vary in the range of 1,800 to 2,000 ft (550 to 610 m) above the city. The device was set to explode at 1,885 ft (575 m), but this was approximate. Malik (1985) uses the figure of 1,903 ft (580 m) plus or minus 50 ft (15 m), determined after data review by Hubbell et al. (1969). Radar returns from the tops of multistory buildings near the hypocenter may have triggered the detonation at a somewhat higher altitude than planned. Kerr et al. (2005) found that a detonation altitude of 600 m (1,968.5 ft), plus or minus 20 m (65.6 ft), gave the best fit for all the measurement discrepancies.

^ ab"The Nuclear Matters Handbook". "For surface and low-air bursts, the fireball will rise quickly, and within approximately one minute, it will be at an altitude high enough that none of the gamma radiation produced inside the fireball will have any impact to people or equipment on the ground. For this reason, initial nuclear radiation is defined as the nuclear radiation produced within one minute post-detonation. Initial nuclear radiation is also called prompt nuclear radiation."